Yet another cancer drug made news at the annual meeting of the American Society of Clinical Oncology. The experimental drug being developed by Bristol-Myers Squibb blocks a protein called PD-1, as reported in the New York Times. The drug has been found to give positive results in the form of tumor shrinkage in three different cancers, lung, skin, and kidney.
Tumor cells have a protective covering which helps them to keep body’s immune system at bay or destroy them. The new drug being discussed, aims to disable this shield of tumor cells and make them vulnerable to the cells of the body’s immune system. The drug, called BMS-936558 blocks PD-1 proteins.
PD-1 is programmed death 1. PD-1 proteins are present on the surface of T cells. When a molecule called PD-L1 binds to PD-1, the T cells die. Thus, body’s immune mechanism is jeopardized. Tumor cells producing PD-L1 are hence capable of disarming the immune system of the body.
The new drug, is a monoclonal antibody, which binds to PD-1 and thereby prevents PD-L1 from binding to PD-1. Now, PD-1 blockers are specific to T cells around tumors and hence T cells are at their active best especially around the tumor cells.
The clinical trial conducted included 296 patients with various cancers in advanced stages. The observed results,
- Tumor shrinkage in 18% of lung cancer patients
- Tumor shrinkage in 28% of melanoma patients
- Tumor shrinkage in 27% of kidney cancer
- Drug had no significant effect in patients with prostate or colon cancer
Even though, 14% of participants complained of one serious side effect and three patients died due to drug related inflammation, the results are a success in the field of guiding body’s own immune system to destroy and fight cancer cells.
PD-1 blockers are specific for tumors that produce PD-L1 and hence, might be useful only in patients who would benefit the most. PD-1 was discovered by Dr. Tasuku Honjo, Kyoto University and colleagues.
The study results will be published in the New England of Journal of Medicine. Dr. Suzanne L. Topalian, melanoma specialist at Johns Hopkins University is the lead investigator of the study.
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